Extra-articular implantable mechanical energy absorbing systems

ABSTRACT

A system and method for sharing and absorbing energy between body parts. In one particular aspect, the system facilitates absorbing energy between members forming a joint such as between articulating bones.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 11/743,097, filed May 1, 2007, the contents of which are incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention is directed towards systems and methods for treating tissue of a body and more particularly, towards approaches designed to reduce mechanical energy transferred between members forming a natural joint.

Both humans and other mammals belong to the subphylum known as vertebrata. The defining characteristic of a vertebrate is considered the backbone or spinal cord, a brain case, and an internal skeleton. In biology, the skeleton or skeletal system is the biological system providing physical support in living organisms. Skeletal systems are commonly divided into three types—external (an exoskeleton), internal (an endoskeleton), and fluid based (a hydrostatic skeleton).

An internal skeletal system consists of rigid (or semi-rigid) structures, within the body, moved by the muscular system. If the structures are mineralized or ossified, as they are in humans and other mammals, they are referred to as bones. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage. Some organisms have a skeleton consisting entirely of cartilage and without any calcified bones at all, for example sharks. The bones or other rigid structures are connected by ligaments and connected to the muscular system via tendons.

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally. Structural classification is determined by how the bones connected to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications.

There are three structural classifications of joints, namely fibrous or immovable joints, cartilaginous joints and synovial joints. Fibrous/Immovable bones are connected by dense connective tissue, consisting mainly of collagen. The fibrous joints are further divided into three types:

-   -   sutures which are found between bones of the skull;     -   syndesmosis which are found between long bones of the body; and     -   gomphosis which is a joint between the root of a tooth and the         sockets in the maxilla or mandible.

Cartilaginous bones are connected entirely by cartilage (also known as “synchondroses”). Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Synovial joints have a space between the articulating bones for synovial fluid. This classification contains joints that are the most mobile of the three, and includes the knee and shoulder. These are further classified into ball and socket joints, condyloid joints, saddle joints, hinge joints, pivot joints, and gliding joints.

Joints can also be classified functionally, by the degree of mobility they allow. Synarthrosis joints permit little or no mobility. They can be categorized by how the two bones are joined together. That is, synchrondoses are joints where the two bones are connected by a piece of cartilage. Synostoses are where two bones that are initially separated eventually fuse together as a child approaches adulthood. By contrast, amphiarthrosis joints permit slight mobility. The two bone surfaces at the joint are both covered in hyaline cartilage and joined by strands of fibrocartilage. Most amphiarthrosis joints are cartilaginous.

Finally, diarthrosis joints permit a variety of movements (e.g. flexion, adduction, pronation). Only synovial joints are diarthrodial and they can be divided into six classes: 1. ball and socket—such as the shoulder or the hip and femur; 2. hinge—such as the elbow; 3. pivot—such as the radius and ulna; 4. condyloidal (or ellipsoidal)—such as the wrist between radius and carps, or knee; 5. saddle—such as the joint between carpal thumbs and metacarpals; and 6. gliding—such as between the carpals.

Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of joints in the body. As with all other joints in the body, synovial joints achieve movement at the point of contact of the articulating bones. Structural and functional differences distinguish the synovial joints from the two other types of joints in the body, with the main structural difference being the existence of a cavity between the articulating bones and the occupation of a fluid in that cavity which aids movement. The whole of a diarthrosis is contained by a ligamentous sac, the joint capsule or articular capsule. The surfaces of the two bones at the joint are covered in cartilage. The thickness of the cartilage varies with each joint, and sometimes may be of uneven thickness. Articular cartilage is multi-layered. A thin superficial layer provides a smooth surface for the two bones to slide against each other. Of all the layers, it has the highest concentration of collagen and the lowest concentration of proteoglycans, making it very resistant to shear stresses. Deeper than that is an intermediate layer, which is mechanically designed to absorb shocks and distribute the load efficiently. The deepest layer is highly calcified, and anchors the articular cartilage to the bone. In joints where the two surfaces do not fit snugly together, a meniscus or multiple folds of fibro-cartilage within the joint correct the fit, ensuring stability and the optimal distribution of load forces. The synovium is a membrane that covers all the non-cartilaginous surfaces within the joint capsule. It secretes synovial fluid into the joint, which nourishes and lubricates the articular cartilage. The synovium is separated from the capsule by a layer of cellular tissue that contains blood vessels and nerves.

Cartilage is a type of dense connective tissue and as shown above, it forms a critical part of the functionality of a body joint. It is composed of collagenous fibers and/or elastin fibers, and cells called chondrocytes, all of which are embedded in a firm gel-like ground substance called the matrix. Articular cartilage is avascular (contains no blood vessels) and nutrients are diffused through the matrix. Cartilage serves several functions, including providing a framework upon which bone deposition can begin and supplying smooth surfaces for the movement of articulating bones. Cartilage is found in many places in the body including the joints, the rib cage, the ear, the nose, the bronchial tubes and between intervertebral discs. There are three main types of cartilage: hyaline, elastic and fibrocartilage.

Chondrocytes are the only cells found in cartilage. They produce and maintain the cartilaginous matrix. Experimental evidence indicates that cells are sensitive to their mechanical (stress-strain) state, and react directly to mechanical stimuli. The biosynthetic response of chondrocytes was found to be sensitive to the frequency and amplitude of loading (Wong et al., 1999 and Kurz et al., 2001). Recent experimental studies further indicate that excessive, repetitive loading may induce cell death, and cause morphological and cellular damage, as seen in degenerative joint disease (Lucchinetti et al., 2002 and Sauerland et al., 2003). Islam et al. (2002) found that continuous cyclic hydrostatic pressure (5 MPa, 1 Hz for 4 hours) induced apoptosis in human chondrocytes derived from osteoarthritic cartilage in vitro. In contrast, cyclic, physiological-like loading was found to trigger a partial recovery of morphological and ultra-structural aspects in osteoarthritic human articular chondrocytes (Nerucci et al., 1999).

Cancellous bone (also known as trabecular, or spongy) is a type of osseous tissue which also forms an important aspect of a body joint. Cancellous bone has a low density and strength but very high surface area, that fills the inner cavity of long bones. The external layer of cancellous bone contains red bone marrow where the production of blood cellular components (known as hematopoiesis) takes place. Cancellous bone is also where most of the arteries and veins of bone organs are found. The second type of osseous tissue is known as cortical bone, forming the hard outer layer of bone organs.

Various maladies can affect the joints, one of which is arthritis. Arthritis is a group of conditions where there is damage caused to the joints of the body. Arthritis is the leading cause of disability in people over the age of 65.

There are many forms of arthritis, each of which has a different cause. Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. The most common form of arthritis, osteoarthritis is also known as degenerative joint disease and occurs following trauma to the joint, following an infection of the joint or simply as a result of aging.

Unfortunately, all arthritides feature pain. Patterns of pain differ among the arthritides and the location. Rheumatoid arthritis is generally worse in the morning; in the early stages, patients often do not have symptoms following their morning shower.

Osteoarthritis (OA, also known as degenerative arthritis or degenerative joint disease, and sometimes referred to as “arthrosis” or “osteoarthrosis” or in more colloquial terms “wear and tear”), is a condition in which low-grade inflammation results in pain in the joints, caused by wearing of the cartilage that covers and acts as a cushion inside joints. As the bone surfaces become less well protected by cartilage, the patient experiences pain upon weight bearing, including walking and standing. Due to decreased movement because of the pain, regional muscles may atrophy, and ligaments may become more lax. OA is the most common form of arthritis.

The main symptoms of osteoarthritis is chronic pain, causing loss of mobility and often stiffness. “Pain” is generally described as a sharp ache, or a burning sensation in the associated muscles and tendons. OA can cause a crackling noise (called “crepitus”) when the affected joint is moved or touched, and patients may experience muscle spasm and contractions in the tendons. Occasionally, the joints may also be filled with fluid. Humid weather increases the pain in many patients.

OA commonly affects the hand, feet, spine, and the large weight-bearing joints, such as the hips and knees, although in theory, any joint in the body can be affected. As OA progresses, the affected joints appear larger, are stiff and painful, and usually feel worse, the more they are used and loaded throughout the day, thus distinguishing it from rheumatoid arthritis. With progression in OA, cartilage looses its viscoelastic properties and it's ability to absorb load.

Generally speaking, the process of clinical detectable osteoarthritis is irreversible, and typical treatment consists of medication or other interventions that can reduce the pain of OA and thereby improve the function of the joint. According to an article entitled Surgical approaches for osteoarthritis by Klaus-Peter Günther, MD, over recent decades, a variety of surgical procedures have been developed with the aim of decreasing or eliminating pain and improving function in patients with advanced osteoarthritis (OA). The different approaches include preservation or restoration of articular surfaces, total joint replacement with artificial implants, and arthrodeses.

Arthrodeses are described as being reasonable alternatives for treating OA of small hand and foot joints as well as degenerative disorders of the spine, but were deemed to be rarely indicated in large weight-bearing joints such as the knee due to functional impairment of gait, cosmetic problems and further side-effects. Total joint replacement was characterized as an extremely effective treatment for severe joint disease. Moreover, recently developed joint-preserving treatment modalities were identified as having a potential to stimulate the formation of a new articular surface in the future. However, it was concluded that such techniques do not presently predictably restore a durable articular surface to an osteoarthritic joint. Thus, the correction of mechanical abnormalities by osteotomy and joint debridement are still considered as treatment options in many patients. Moreover, patients with limb malalignment, instability and intra-articular causes of mechanical dysfunction can benefit from an osteotomy to provide pain relief. The goal being the transfer of weight-bearing forces from arthritic portions to healthier locations of a joint.

Joint replacement is one of the most common and successful operations in modern orthopaedic surgery. It consists of replacing painful, arthritic, worn or diseased parts of the joint with artificial surfaces shaped in such a way as to allow joint movement. Such procedures are a last resort treatment as they are highly invasive and require substantial periods of recovery. Joint replacement sometimes called total joint replacement indicating that all joint surfaces are replaced. This contrasts with hemiarthroplasty (half arthroplasty) in which only one bone's joint surface is replaced and unincompartmental arthroplasty in which both surfaces of the knee, for example, are replaced but only on the inner or outer sides, not both. Thus, arthroplasty as a general term, is an operative procedure of orthopaedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure. These procedures are also characterized by relatively long recovery times and their highly invasive procedures. The currently available therapies are not condro-protective. Previously, a popular form of arthroplasty was interpositional arthroplasty with interposition of some other tissue like skin, muscle or tendon to keep inflammatory surfaces apart or excisional arthroplasty in which the joint surface and bone was removed leaving scar tissue to fill in the gap. Other forms of arthroplasty include resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, silicone replacement arthroplasty, etc. Osteotomy to restore or modify joint congruity is also an arthroplasty.

Osteotomy is a related surgical procedure involving cutting of bone to improve alignment. The goal of osteotomy is to relieve pain by equalizing forces across the joint as well as increase the lifespan of the joint. This procedure is often used in younger, more active or heavier patients. High tibial osteotomy (HTO) is associated with a decrease in pain and improved function. However, HTO does not address ligamentous instability—only mechanical alignment. HTO is associated with good early results, but results deteriorate over time.

Other approaches to treating osteoarthritis involve an analysis of loads which exist at a joint. Both cartilage and bone are living tissues that respond and adapt to the loads they experience. If a joint surface remains unloaded for appreciable periods of time the cartilage tends to soften and weaken. Further, as with most materials that experience structural loads, particularly cyclic structural loads, both bone and cartilage begin to show signs of failure at loads that are below their ultimate strength. However, cartilage and bone have some ability to repair themselves. There is also a level of load at which the skeleton will fail catastrophically. Accordingly, it has been concluded that the treatment of osteoarthritis and other conditions is severely hampered when a surgeon is not able to precisely control and prescribe the levels of joint load. Furthermore, bone healing research has shown that some mechanical stimulation can enhance the healing response and it is likely that the optimum regime for a cartilage/bone graft or construct will involve different levels of load over time, e.g. during a particular treatment schedule. Thus, there has been identified a need for devices which facilitate the control of load on a joint undergoing treatment or therapy, to thereby enable use of the joint within a healthy loading zone.

Certain other approaches to treating osteoarthritis contemplate external devices such as braces or fixators which control the motion of the bones at a joint or apply cross-loads at a joint to shift load from one side of the joint to the other. Various of these approaches have had some success in alleviating pain but suffer from patient compliance or lack an ability to facilitate and support the natural motion and function of the diseased joint. Notably, the motion of bones forming a joint can be as distinctive as a finger print, and thus, each individual has his or her own unique set of problems to address. Therefore, mechanical approaches to treating osteoarthritis have had limited applications.

Prior approaches to treating osteoarthritis have also been remiss in acknowledging all of the basic functions of the various structures of a joint in combination with its unique movement. That is, in addition to addressing loads at a joint and joint movement, there has not been an approach which also acknowledges the dampening and energy absorption functions of the anatomy, and taking a minimally invasive approach in implementing solutions. Prior devices designed to reduce the load transferred by the natural joint typically describe rigid body systems that are incompressible. Mechanical energy is the product of force (F) and displacement distance (s) of a given mass (i.e., E=Fxs, for a given mass M). These systems have zero displacement within their working body (s=0). Since there is no displacement within the device it is reasonable to say that there is no energy storage or absorption in the device. Such devices act to transfer and not absorb energy from the joint. By contrast the natural joint is not a rigid body but is comprised of elements of different compliance characteristics such as bone, cartilage, synovial fluid, muscles, tendons, ligaments, etc. as described above. These dynamic elements act to both transfer and absorb energy about the joint. For example cartilage compresses under applied force and therefore the resultant force displacement product represents the energy absorbed by cartilage. In addition cartilage has a non linear force displacement behavior and is considered viscoelastic. Such systems not only absorb and store, but additionally act to dissipate energy.

Therefore, what is needed and heretofore lacking in prior attempts to treat joint pain is an approach which addresses both joint movement and varying loads as well as dampening forces and energy absorption provided by an articulate joint.

The present invention satisfies these and other needs.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed towards treating diseased or mal-aligned body components. In one aspect, the present invention is embodied in methods and devices for treating and preserving body joints. In one aspect of treating and preserving body joints, the present invention is embodied in methods and devices implanted under the patient's skin for relieving joint pain that do not require modification of articular cartilage. In a preferred aspect, the device is implanted under the patient's skin but outside of the joint capsule. In a particular aspect, the joint pain is caused by osteoarthritis.

In one embodiment, the present invention addresses the pain associated with joint disease and mal-alignment. In presently contemplated embodiments, a minimally invasive approach is taken to alleviate pain while preserving full motion of the bones forming a joint. The devices of the present invention accomplish one or more of: absorbing energy during normal gait, reducing load on at least a portion of the natural joint, load transferring or bypassing, energy cushioning, and load sharing or redistribution. In addition, both energy dampening and shock absorption are considered in effecting such load manipulations. Further, the particular anatomy of a patient is considered in the contemplated approaches in that loads on desired portions of anatomy are manipulated without overloading healthy surfaces. It is believed that employing the approaches of the present invention can slow the progression of disease affecting the joint and can further improve alignment, stability, or support or enhance medial collateral ligament (MCL) or lateral collateral ligament (LCL) function.

In a preferred embodiment, the present invention adds an energy absorber to the joint to reduce energy transferred through the natural joint.

The present invention can be used unilaterally, bilaterally or multi-laterally around a body joint.

The present invention has the capacity to absorb energy in addition to transfer energy from the joint. The simplest embodiment of the present invention incorporates a linear elastic spring. The energy absorption of the spring can be expressed as the product of force and displacement. In addition to a linear spring element, non linear spring members can be employed to alter the energy absorption behavior under the same loading or displacement conditions. Although actual springs are used to show various embodiments of the present invention, these elements could also be substituted with a material or other device with spring-like characteristics (e.g., an elastomeric member).

In other embodiments, spring systems may be coupled with dampening devices such as dash pots. In these embodiments, the spring element is a storage or absorber device while the dashpot acts to dissipate the energy from the spring. Such embodiments alter the velocity of displacement of the spring, thereby altering the energy absorption behavior. Although more traditional dampening devices are used to show various embodiments of the present invention, these elements could also be substituted with a material or other device with dampening characteristics (e.g., a small pore sponge).

The operations of these embodiments and the prior art rigid systems can be described graphically using force versus displacement diagrams (mass is assumed constant). Thus a rigid body system that allows no displacement, no energy absorbed by the device, can be compared with a simple linear spring system of the present invention where energy is absorbed in proportion to a spring constant (i.e., stiffness of the spring) as well to spring and dampener combination systems where the energy absorbed is a function of the spring constant and the dampener.

One particular beneficial aspect of the energy absorption systems of the present invention are that they are capable of absorbing a constant amount of energy from the joint independent of joint kinematics or loading conditions. In contrast, the rigid body systems of the prior art (such as a cam system) are based on the physician separating (i.e., distracting) the natural joint a given distance in the unloaded state and attaching the rigid body system. The rigid body system then maintains this distance/distraction throughout the gait cycle and through bending of the joint. To maintain this distraction, the rigid body must transfer a wide range of forces directly depending on joint kinematics.

Another particularly beneficial aspect of the energy absorption system of the present invention is that the absorption system may be designed to absorb, dissipate and/or transfer energy at different rates or positions in the gait cycle thereby enabling customization of the system to the specific need. Considering the knee joint by way of example, if a spring system is coupled to a dampener to create a viscoelastic body, the system may be designed to absorb severe sudden impact loads (such as jumping) and dissipate these loads after the impact event. This mode of operation is akin to the natural role of cartilage. Conversely, the system can be designed to behave primarily as an energy transfer unit during high rates of knee motion (e.g. sprinting/running) but act as an energy absorber during normal rates of motion (e.g. walking).

Yet another particularly beneficial aspect of the energy absorption system of the present invention is that the absorption system may also be tuned to occur at particular points in the gait or flexion cycle depending on the disease state. For example an individual with concentrated loading at heel strike may only require absorption at this phase of knee motion so the system may be adjusted to act only during this region of the gait cycle. Alternatively an individual may have focal loss of cartilage on the posterior aspect of the femoral condyle and so stair climbing or kneeling becomes painful or problematic. In this scenario the system would be adjusted to absorb energy in the kinematic positions necessary and thereby maintaining the normal knee energy transfer outside of supporting the diseased locations.

In another beneficial aspect of the present invention, components of the system are designed for easy removal and, if necessary, replacement while others are intended for permanent fixation. The permanent components are fixation attachment structures which can have bony ingrowth promoting surfaces and are responsible for fixation of the system to the skeletal structure. The removable components include the mobile elements of the system such as the link members and/or the pivots or ball joints.

Various joints of the body can be treated employing the systems and methods of the present invention. In particular, articulating bones involved in synovial joints can benefit from the present invention. Accordingly, there are contemplated applications to the joints in the knee, ankle, shoulder, hip, hand and wrist. Further, the present invention can have applications in treating cartilaginous joints such as those found in the spine.

In a further aspect, the present invention seeks to accomplish 1 to 40% energy or load reduction while maintaining full motion of the body parts. A 5 to 20% energy or load reduction has been postulated to be desirable in certain circumstances to accomplish the alleviation of pain without approaching undesirable load shielding. The devices of the present invention further provide greater energy manipulation during junctures of highest loads placed between body parts as well as less energy manipulation when loads between members decrease. In this way, the present invention complements the action of body parts such as those found at joints.

In some joints, it is desirable that 100% of the energy be absorbed by the device(s), such joints may be those in the hands or upper extremity. In such cases, it may be desirable to have the devices placed bilaterally on either side of the joint. In the lower extremity, in severe cases, 100% energy absorption is achievable, however this may expose the device to more wear and shorter life. Some patients may accept this if the device is able to bridge the patient through a difficult period and it is easily replaced or removed without impacting the patients ability to receive a total joint replacement later.

In another embodiment of the present invention, an energy absorption device is implanted at a diseased joint to restore cyclic, physiological-like loading thereby protecting chondrocytes from load induced apoptosis.

In yet another embodiment of the present invention, an energy absorption device is implanted at a diseased joint to facilitate at least a partial recovery of morphological and ultra-structural aspects in osteoarthritic articular chondrocytes.

In another embodiment of the present invention, an energy absorption device is implanted adjunctively with a cartilage repair procedure such as mosaicplasty, osteochondral allograft transfer, autologous chondrocyte implantation or microfracture. Such an adjunctive procedure would enable less strict rehabilitation regimes while simultaneously protecting the graft and stimulating it with appropriate motion.

In another embodiment of the present invention, an energy absorption device is implanted in conjunction with a uni-compartmental joint replacement prosthesis or total joint replacement prosthesis. Such combination procedure will reduce wear rates by reducing the loads and contact forces between surfaces of the joint prosthesis.

In one specific embodiment, the present invention is embodied in a device utilizing an element, or elements functioning as a unit, which responds to bending or changes in elongation. In an application to a knee joint, this device forms a bending spring that is to span the tibiofemoral joint and be anchored into the tibia and femur. Further, the device is used to take on some of the loading experienced by the articular surfaces of the tibiofemoral joint, thus unloading the joint. In one embodiment, the device is designed to off load the joint during knee extension. Unloading in this phase is governed by the compression of the device—increased compression yields increased joint un-loading. The device is anchored in a position which ensures device elongation resulting from knee flexion. As the knee moves into flexion, the device is un-compressed and will cause little to no joint off-loading. The device may have other features which ensure correct device alignment, and prevent against buckling, as the device transitions into a compressed state. The device can also be configured to provide off-loading during flexion.

In another specific approach, the present invention is embodied in a cam engagement assembly utilizing contacting elements, at least one of which having an eccentric contacting surface. The element, or elements, possessing the eccentric surface define a cam. Again in an application to the knee joint, one element is anchored to the femur and the other to the tibia. Implanted, the device will span the tibiofemoral joint. The degree, duration, and instance of elemental contact is dictated by the profile of the cam element or elements. In one embodiment, the cam is designed to cause increased contact stress between the device elements which span the joint when the knee is in extension. During instances of increased contact stress, the normal energy experienced by the articular surfaces of the tibiofemoral joint will be absorbed and taken on, in part, by the device. During instances of knee flexion, the cam profile will ensure little or no engagement leading to joint off-loading. Thus, the amount of energy absorption will be controlled by a spring element which backs the cam element. The spring element can be adjusted, or exchanged, to tune the amount of energy absorption across the joint.

In yet another specific approach, a segmented support assembly is employed to address joint needs. This concept utilizes multiple elements that align to provide columnar support at desired phases of knee movement. In one application, the device is designed to provide columnar support during phases of knee extension. That is, each element is constrained by the adjacent element in a variable fashion—least constrained during states of elongation and most constrained during states of compression. The variable motion constraint, or tolerance which increases with elongation, is designed so that the cumulative effect is to accommodate the complex motion of the tibiofemoral joint for example as it transitions from extension into flexion. The device is anchored, via mounting components, in a way that dictates device elongation during knee flexion and device compression during knee extension. During the state of device compression, the device will experience part of the energy normally taken on by the articular surfaces of the tibiofemoral joint—thus reducing the energy absorbed by the joint by a desired amount. The amount of energy absorption can be adjusted, via the mounting components, to a desired and measurable amount. The assembly will accommodate the transition from an unloaded to a loaded state by the use of elements, possessing either spring or dampening characteristics, either in the device mounting components or in between the mating surfaces of the device elements.

In a further approach, the invention is embodied in a piston support assembly. This approach employs a spring loaded piston mechanism to absorb energy normally experienced by the anatomical joint. The piston is comprised of an axially mobile member or rod moving in a defined path. Depending on the axial position of the rod, a compressible spring is engaged thereby transferring load through the mechanism. When the spring is not engaged no absorbing or load transfer occurs. The device may utilize rigid and coaxial elements that ride into or through each other. Load transfer and energy absorption occurs when the spring is engaged. For this system to function without hindering the range of motion of the knee for example, the fixation points between bone and piston mechanism are free to revolve about an axis (possibly multiple axes). In addition, the piston is capable of rotating about its longitudinal axis to facilitate rotational along the axis of the anatomical joint.

The present invention also includes a staged procedure. In this aspect, the energy absorption system is comprised of permanent fixation attachment structures and removable links. The permanent fixation attachment structures incorporate a bone ingrowth promoter on their bone contacting surface (e.g. porous surface, calcium phosphate coating, textured surface etc.). It is important to stimulate this interface using moderate loads to ensure the creation of a bony interface, however overloading the interface prematurely may prevent bone ingrowth. To facilitate bony ingrowth, it is possible that the system will be implanted in a mode of operation whereby it is absorbing small amounts of load to create a moderate load condition at the interface. A subsequent simple procedure will be completed at an appropriate time post implantation to adjust the energy absorption settings to absorb higher amounts of load.

The present invention also contemplates intra-articular drug delivery in combination with joint energy and load manipulation. In one contemplated approach, a drug release device is loaded with a drug and a sustained released drug carrier, and placed at a target area within or near a diseased or malaligned joint, such as on or in the device of the present invention. Various drugs and mechanisms for sustained release are also contemplated.

Moreover, in certain aspects, the present invention also contemplates employing sensors to provide information on performance. For example, pressure sensors can be placed within or adjacent the device or anatomy to indicate aspects of function and loads. Sensors in the implant may allow for non-invasive telemetry and capture of information regarding joint motion. Telemetry may be usable to control various settings in the device.

The present invention also contemplates that the components are compatible with joint diagnostic techniques such as magnetic resonance imaging and computed tomography.

Additionally, the present invention contemplates post-operative percutaneous adjustability and tuning of the implant's characteristics in response to patient feedback. It may be desirable to detect the internal tension and/or dampening setting of the device while it is being accessed percutaneously or alternatively have those features easily detectable using x-ray or another non-invasive modality such as ultrasound.

Another aspect of some embodiments of the present invention is to enclose at least a part of the energy manipulating device in a sheath. The sheath allows the tendons and soft tissue to avoid being abraded by the presence of the implant in that region during movement. By allowing the tissue to form a capsule around the sheath of the implant, the tissue will be strengthened and the likelihood of erosion will be reduced. The sheath also allows for easy replaceability, in some embodiments, of the link components because they can be inserted into the sheath once the original components are removed without causing any additional tissue disruption.

Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, depicting a energy manipulation assembly of the present invention;

FIG. 2 is a side view, depicting the assembly of FIG. 1 after articulation of body members;

FIG. 3 is a front view, depicting a bilateral (or lateral and medial) application of a lower manipulation assembly of the present invention;

FIG. 4 is a side view, depicting a bending spring energy manipulation assembly of the present invention;

FIG. 5 is a side view, depicting the assembly of FIG. 4 after articulation of body members;

FIG. 6 is a front view, depicting the energy manipulation assembly of FIG. 4;

FIG. 7 is a side view, depicting a energy manipulation assembly including a pair of springs;

FIG. 8 is a side view, depicting the assembly of FIG. 7 after articulation of body members;

FIG. 9 is a perspective view, depicting a bending spring energy manipulation assembly including a guide shaft;

FIG. 10 is a side view, depicting a energy manipulation assembly including locking structure;

FIG. 11 is a side view, depicting an energy absorbing spring assembly including undulations configured along a helical path;

FIG. 12 is a perspective view, depicting a energy manipulation assembly including load bearing members and a central spring;

FIG. 13 is a perspective view, depicting another embodiment of a bending spring assembly with a midsection spring;

FIG. 14 is a front view, depicting yet another energy manipulation assembly including a central spring;

FIG. 15 is a perspective view, depicting a yet further bending spring assembly with a central spring;

FIG. 16 is a perspective view, depicting a bending spring assembly including a stop member;

FIG. 17 is a perspective view, depicting the bending spring assembly of FIG. 16 in its compressed configuration;

FIG. 18 is a perspective view, depicting adjustable attachment structure of a energy manipulation assembly;

FIG. 19 is a partial cross-sectional view, depicting dampening structure of an attachment assembly;

FIG. 20 is a perspective view, depicting another embodiment of an attachment structure of a load bearing member;

FIG. 21 is a cross-sectional view, depicting mounting structure formed in body anatomy;

FIG. 22 is a partial cross-sectional view, depicting a energy manipulation assembly affixed to the body anatomy shown in FIG. 21;

FIG. 23 is a cross-sectional view, depicting a load bearing assembly contained substantially entirely within body anatomy;

FIG. 24 is a side view, depicting an enlarged view of the energy manipulation assembly shown in FIG. 23;

FIG. 25 is a side view, depicting a bending spring energy manipulation assembly including a slot for articulating movement;

FIG. 26 is a side view, depicting another embodiment of a bending spring assembly including pivoting structure;

FIG. 27 is a side view, depicting yet a further embodiment of a bending spring assembly including pivoting structure;

FIG. 28 is a perspective view, depicting a energy manipulation assembly incorporating cam engagement structure;

FIG. 29 is a side view, depicting the load bearing assembly shown in FIG. 28;

FIG. 30 is a perspective view, depicting yet another embodiment of a energy manipulation assembly;

FIG. 31 is a perspective view, depicting a energy manipulation assembly including multiple camming surfaces;

FIG. 32 is a front view, depicting a energy manipulation assembly including camming surfaces and spring biasing structure;

FIG. 33 is a perspective view, depicting yet another embodiment of a energy manipulation assembly including multiple camming surfaces;

FIG. 34 is a front view, depicting a energy manipulation assembly including camming surfaces and pivoting substructure;

FIG. 35 is a partial cross-sectional view, depicting a ball bearing in combination with camming surfaces;

FIG. 36 is a side view, depicting a energy manipulation assembly employing a ball-like camming surface;

FIG. 37 is a side view, depicting the assembly of FIG. 37 in relation to articulated body members;

FIG. 38 is a front view, depicting a energy manipulation assembly incorporating segmented support substructure;

FIG. 39 is a side view, depicting the assembly shown in FIG. 38 further incorporating a slotted engagement arrangement;

FIG. 40 is a perspective view, depicting another embodiment of a segmented support subassembly;

FIG. 41 is a perspective view, depicting yet another embodiment of a segmented support subassembly;

FIG. 42 is a perspective view, depicting yet still another segmented support subassembly;

FIG. 43 is a side view, depicting members forming a segmented support subassembly;

FIG. 44 is a perspective view, depicting disengaged members of a segmented support subassembly;

FIG. 45 is a perspective view, depicting a segmented support assembly encased in an outer sheath;

FIG. 46 is a perspective view, depicting both a longitudinally arranged segmented support assembly and its configuration upon bending;

FIG. 47 is a perspective view, depicting a segmented support assembly including variable interlocking links in combination with spring assemblies;

FIG. 48 is a side view, depicting yet another embodiment of a segmented energy manipulation assembly;

FIG. 49 is a side view, depicting still yet another embodiment of a segmented energy manipulation assembly;

FIG. 50 is a partial cross-sectional side view, depicting still yet another segmented support assembly for a energy manipulation assembly;

FIG. 51 is a partial cross-sectional view, depicting the assembly of FIG. 50;

FIG. 52 is a bottom view, depicting the assembly shown in FIG. 50;

FIG. 53 is a side view, depicting a segmented energy manipulation assembly including slotted attachment structure;

FIG. 54 is a side view, depicting a modification to the assembly shown in FIG. 53;

FIG. 55 is a front view, depicting a energy manipulation assembly incorporating segmented and articulating structure;

FIG. 56 is a side view, depicting sheathing of members of a energy manipulation assembly;

FIG. 57 is a perspective view, depicting further aspects of a segmented support assembly of the present invention;

FIG. 58 is a side view, depicting yet further aspects of segmented support assemblies of the present invention;

FIG. 59 is a side view, depicting a energy manipulation assembly including articulating and segmented structure;

FIG. 60 is a front view, depicting a energy manipulation assembly incorporating piston support;

FIG. 61 is a side view, depicting the assembly of FIG. 60 after articulation of body members;

FIG. 62 is a front view, depicting another embodiment of a energy manipulation assembly incorporating piston support;

FIG. 63 is a cross-sectional view, depicting substructure of the assembly shown in FIG. 62;

FIG. 64 is a partial cross-sectional view, depicting another embodiment of a piston support subassembly;

FIG. 65 is a partial cross-sectional view, depicting yet another embodiment of a piston support subassembly;

FIG. 66 is a perspective view, depicting still yet another embodiment of a piston support subassembly;

FIG. 67 is a perspective view, depicting the assembly of FIG. 66 in a compressed configuration;

FIG. 68 is a perspective view, depicting a further embodiment of a energy manipulation assembly incorporating piston support structure;

FIG. 69 is a perspective view, depicting a telescoping arrangement of a piston support subassembly;

FIG. 70 is a perspective view, depicting the assembly of FIG. 69 in a compressed configuration;

FIG. 71 is a cross-sectional view, depicting a energy manipulation assembly substantially completely imbedded within body tissue;

FIG. 72 is a cross-sectional view, depicting another approach to a energy manipulation assembly substantially completely imbedded within body tissue;

FIG. 73 is a cross-sectional view, depicting a first step in the implantation of a energy manipulation assembly incorporating piston support;

FIG. 74 is a cross-sectional view, depicting a second step in the implantation of the assembly shown in FIG. 73;

FIG. 75 is a perspective view, depicting a load bearing member of a energy manipulation assembly including piston support and incorporating rotational substructure;

FIG. 76 is a perspective view, depicting adjustment substructure of a energy manipulation assembly for the present invention;

FIG. 77 is a cross-sectional view, depicting further aspects of the assembly depicted in FIG. 76;

FIG. 78 is a perspective view, depicting further aspects which can be incorporated into the assembly depicted in FIG. 76;

FIG. 79 is a perspective view, depicting adjustment structure of a energy manipulation assembly of the present invention;

FIG. 80 is a cross-sectional view, depicting a first step in the implantation of a sheathed energy manipulation assembly;

FIG. 81 is a cross-sectional view, depicting a second step in an implantation approach of the assembly depicted in FIG. 80;

FIG. 82 is a cross-sectional view, depicting the assembly of FIG. 81 fully implanted;

FIG. 83 is a cross-sectional view, depicting an enlarged view of an implanted energy manipulation assembly including piston support;

FIG. 84 is a cross-sectional view, depicting an alternate embodiment of a energy manipulation assembly incorporating piston support implanted within body anatomy;

FIG. 85 is a cross-sectional view, depicting further substructure which may be incorporated into the assembly depicted in FIG. 84;

FIG. 86 is a cross-sectional view, depicting another embodiment of a energy manipulation assembly of the present invention incorporating piston support substructure;

FIG. 87 is a perspective view, depicting a energy manipulation assembly including lateral substructure spanning a width of treated body tissue;

FIG. 88 is an enlarged view, depicting substructure of the device depicted in FIG. 87;

FIG. 89 is an enlarged view, depicting substructure of the device depicted in FIG. 87;

FIG. 90 is a cross-sectional front view, depicting the assembly of FIG. 87;

FIG. 91 is a cross-sectional view, depicting yet another component of the assembly depicting in FIG. 87;

FIG. 92 is a perspective view, depicting a further embodiment of a energy manipulation assembly incorporating piston support;

FIG. 93 is a cross-sectional view, depicting substructure of the assembly depicted in FIG. 92;

FIG. 94 is a cross-sectional view, depicting other substructure of the assembly depicted in FIG. 92;

FIG. 95 is a back view, depicting yet another approach for an energy manipulation assembly;

FIG. 96 is a perspective view, depicting the approach shown in FIG. 95;

FIG. 97 is a side view, depicting a further embodiment of an energy manipulation assembly of the present invention;

FIG. 98 is a perspective view, depicting a bilateral approach of the present invention;

FIG. 99 is a perspective view, depicting another bilateral approach of the present invention;

FIG. 100 is a perspective view, depicting an embodiment of the present invention where the body anatomy is aligned;

FIG. 101 is a perspective view, depicting the embodiment of FIG. 100 with the body anatomy in an articulated configuration;

FIG. 102 is a perspective view, depicting an embodiment of the present invention incorporating pivoting and disengaging structure;

FIG. 103 is a perspective view, depicting the embodiment of FIG. 102 with the anatomy in an articulated position;

FIG. 104 is a perspective view, depicting yet another embodiment of mounting structures attached to body anatomy;

FIG. 105 is a perspective view, depicting still yet another embodiment of mounting structure attached to body anatomy;

FIG. 106 is a perspective view, depicting yet another approach to an energy manipulation assembly;

FIG. 107 is a side view, depicting the normal forces existing in a joint;

FIG. 108 is a side view, depicting the present invention incorporated into the joint shown in FIG. 108;

FIG. 109 is a side view, depicting the effect an energy manipulating assembly of the present invention has on the joint shown in FIGS. 107 and 108;

FIG. 110 is a graph, illustrating the energy characteristics of a prior art rigid structure applied across a joint;

FIG. 111 is a graph, illustrating the energy characteristics of a linear spring system of the present invention;

FIG. 112 is a graph, illustrating the energy characteristics of a spring and dampening system of the present invention; and

FIG. 113 is a graph, illustrating the flexion/extension angle and joint force existing in a gait cycle;

FIG. 114 is a graph, illustrating one approach to energy absorption on a gait cycle;

FIG. 115 is a graph, illustrating a second approach to energy absorption on a gait cycle;

FIG. 116 is a graph, illustrating a third approach to energy absorption on a gait cycle;

FIG. 117 is a graph, illustrating a fourth approach to energy absorption on a gait cycle;

FIG. 118 is an isometric view, depicting another energy manipulation assembly of the present invention.

FIG. 119 is a perspective view, depicting the application of the present invention to another body joint;

FIG. 120 is an enlarged view, depicting the energy manipulation assembly of FIG. 119;

FIG. 121 is a side view, depicting the application of the present invention to a foot joint;

FIG. 122 is a top view, depicting the application of the present invention to a finger joint;

FIG. 123 is a side view, depicting an alternate to the approach shown in FIG. 122;

FIG. 124 is a perspective view, depicting the application of the present invention to a spinal joint; and

FIG. 125 is a perspective view, depicting another application of the present invention to a spinal joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, which are provided by way of example and not limitation, the present invention is directed towards apparatus and methods for treating body tissues. In applications relating to the treatment of body joints, the present invention seeks to alleviate pain associated with the function of diseased or malaligned members forming a body joint. Whereas the present invention is particularly suited to address issues associated with osteoarthritis, the energy manipulation accomplished by the present invention lends itself well to broader applications. Moreover, the present invention is particularly suited to treating synovial joints such as the knee and shoulder. However, it is also contemplated that the apparatus and method of the present invention can be employed to treat the spine facet joints and spine vertebral joints as well as other synovial and various other joints of the body such as those of the hand and feet.

In one particular aspect, the present invention seeks to permit and complement the unique articulating motion of the members defining a body joint of a patient while simultaneously manipulating energy being experienced by both cartilage and osseous tissue (cancellous and cortical bone). Approaches involving varying energy absorption and transfer during the pivoting of the joint and selecting a geometry for the energy absorption assembly to provide necessary flexibility are implemented into various embodiments of the present invention. Certain of the embodiments include geometry which accomplishes variable energy absorption designed to minimize and complement the dampening effect and energy absorption provided by the anatomy of the body, such as that found at a body joint. It has been postulated that to minimize pain, off-loading or absorption of 1-40% of forces, in varying degrees, may be necessary. Variable off-loading or absorption in the range of 5-20% can be a target for certain applications. In certain specific applications, distraction is employed in the energy manipulation approach.

Conventional or surgical or minimally invasive approaches are taken to gain access to a body joint or other anatomy requiring attention. Arthroscopic approaches are thus contemplated when reasonable to both implant the energy manipulation assembly as well as to accomplish adjusting an implanted assembly. Moreover, biologically inert materials of various kinds can be employed in constructing the energy manipulation assemblies of the present invention.

In one particular approach, a bending spring assembly is contemplated to manipulate or absorb forces between body parts. Thus, an assembly utilizing an element or elements which respond to bending or changes in elongation may be desirable to treat afflictions such as osteoarthritis. Certain of the assemblies can incorporate features which insure correct device alignment and prevent against buckling as the member transitions between compressed and uncompressed states.

As shown in FIGS. 1 and 2, one embodiment of a bending spring assembly 100 can be configured along members forming a body joint 102. The bending spring assembly 100 includes one or more attachment structures 104, 106 and a energy absorbing member 108. The attachment structures 104, 106 are anchored to the members or bones forming the body joint 102. The energy absorbing member 108 is in the form of a bending spring and is attached to each of the attachment structures 104, 106. While the members defining the joint 102 are generally longitudinally arranged, the energy absorbing member 108 absorbs and/or transfers forces being bared by the members of the joint. In a simplified approach, the energy absorbing member 108 can also apply lateral forces to the member of the joint 102 during flexion.

As shown in FIGS. 1 and 2, a bending spring assembly can be affixed to either a lateral or medial side of a body joint 102. Furthermore, as depicted in FIG. 3, and as well as with each of the disclosed embodiments, bending spring assemblies can additionally be placed on both lateral and medial (or bilateral) surfaces of a body joint 102. Moreover, the energy manipulation achieved by a system of a plurality of bending spring assemblies 100 can be configured to provide different energy manipulation on opposing sides of a joint 100 to thereby accomplish a more complex energy absorption curve and where desired variable off-loading, while permitting and complementing the unique path of motion of the members of a joint of a particular patient.

One particular approach to providing variable energy manipulation while complementing the unique motion of members defining a joint is depicted in FIGS. 4-6. A energy absorbing assembly including an undulating spring member 110 having a variable path can be attached to members defining a body joint 102. The variability of the path is selected to provide additional dampening and/or energy absorption to thus off-load one or more of the cartilage or osseous bones of the joint. Moreover, the energy absorbing spring assembly 110 can be configured to provide such energy manipulation during extension and to become less active during flexion of the members of a joint 102.

Turning now to FIGS. 7 and 8, there is shown another approach to energy manipulation employing a bending spring approach. Here, the bending spring assembly 112 includes a pair of springs attached on the same side of a body joint 102. In this approach, the springs can provide energy manipulation in both flexion and in extension. As shown in FIG. 7, the compressed spring provides central off-loading in a direction normal to joint structure and the extended spring is uncompressed so as to not distract a posterior section of the joint. When the members of the joint are in flexion (FIG. 8), the posterior spring provides energy manipulation normal to the direction of the lateral member of the joint while the centrally located spring provides no off-loading. Other combinations of bend spring assemblies 112 are further contemplated to accomplish other energy manipulation scenarios which may be useful in minimizing joint pain.

Further specific geometries of bending spring assemblies are depicted in FIGS. 9-17. Each of these devices contemplate approaches to energy manipulation which complement the unique motion of a joint of a particular patient. In a first embodiment, the bending spring assembly 114 includes a helical spring 116 configured about a guiding member 118. The helical spring 116 is further configured between anchor points 120 which are affixed to a patient's anatomy. As the members defining a body joint articulate, the anchor points 120 move with respect to each other, the guiding member 118 providing a controlled path for the spring 116 and the spring 116 thereby provides the desired energy absorption and/or load transfer.

As shown in FIG. 10, a helical spring 122 of a bending spring assembly can include interlocking structure 124 which alters the function of the spring 122. For example, the interlocking structure can be adapted to prevent rotation of the spring 122 at a predetermined amount of compression or extension of the spring 122. Thus, a variable energy manipulation can be provided by this structure. Moreover, such structure can alternatively or additionally be employed to prevent or control joint rotation at a given degree of extension or flexion.

A spring assembly 126 having an overall helical configuration is depicted in FIG. 11. This spring assembly 126 further includes undulations 128 configured along the general helical framework as well as sections with varying thickness. In these ways, the spring assembly 126 can provide a varying energy absorption profile which matches the needs of a particular body joint, providing energy manipulation during certain pre-determined phases of articulation of members defining the joint. Similarly, a spring assembly can include spring portions divided by a center section including an elastomeric sleeve (not shown) which provides the device with desired energy manipulation characteristics. Moreover, the elastomeric sleeve can be used in affixing the assembly at the joint requiring treatment.

In related approaches (FIGS. 12-14), a mid-section of the bending spring assembly includes a spring member 136. Opposing ends of the assembly include bone anchors 138. As shown, the opposing ends can include one or more attachment structures or bone anchors 138. Configured between the bone anchor structure 138 and on opposing sides of the central spring 136 are load transfer beams 140. By way of a pivot configured between the bone anchors 140 and beams 140, the load transfer beams 140 can be made to rotate with respect to the bone anchors 138 and each other.

The bending spring assembly 142 depicted in FIG. 15 also includes a centrally located spring 144 configured between a pair of load transfer beams 146. As with previous embodiments, the spring 144 can assume various profiles characterized by varying widths and pitches to thereby provide the desired energy manipulation profile.

FIGS. 16 and 17 depict yet another embodiment of a bending spring assembly 148. In this embodiment, the energy is absorbed initially by an undulating beam 150. Upon near complete compression of the beam 150, curved portions thereof engage a centrally located stop member 152. The stop member 152 can be formed of rigid or non-rigid material depending on the energy manipulation that is desired in the application at hand.

Referring now to FIGS. 18-20, there are shown various details associated with attachment or mounting structure of a bending spring assembly, but the assembly can be employed across all contemplated approaches. A rod 154 connected to one such bend spring assembly (not shown) can be coupled to a bracket assembly 156 which is affixed to body anatomy of a patient. By way of an adjustment screw 156, the placement of the rod 154 can be adjusted with respect to the bracket assembly 156. It is contemplated that a needle screw (not shown) could be employed to accomplish the necessary adjustment percutaneously. The bracket assembly 156 can further or alternatively include a spring 158 (FIG. 19), the tension of which can be adjusted percutaneously to provide desired dampening or shock absorption at the ends of a bending spring assembly. Moreover, the bracket assembly 156 for these any of the disclosed embodiments can further include a textured surface 160 adapted for attachment to patient anatomy. Such texturing can surface irregularities or can come in the form of materials adapted for tissue in-growth.

Furthermore, the bending spring assemblies and for that matter each of the disclosed embodiments of energy manipulation assemblies, can be attached to body anatomy in various ways. As shown above, the assemblies of the present invention can be surface mounted upon anatomy by employing anchors. Also, mounting structure 162 can be inserted completely or partially within bones 163, for example, such as that in the manner depicted in FIGS. 21 and 22. Further anchoring of the assemblies can occur through a surface of the bone (See FIG. 22). Moreover, as shown in FIGS. 23 and 24, a energy manipulation assembly 164 can be placed substantially entirely with a bone 163, leaving a terminal end thereof to accomplish desired energy transfer and/or absorption.

The bending spring assemblies can embody rather complex structures. As shown in FIG. 25, one contemplated bend spring assembly 166 including a spring 168 can be attached to a pair of spaced attachment structures 170, 172. Such attachment structures 170, 172 can be directly connected to body anatomy or can be further attached to structure mounted on or within anatomy. The spring 168 includes one end which is fixed or rotatably connected to a first attachment structure 170 and a second end is constrained within a curved slot formed in the second attachment structure 172. Again, this unique design is contemplated to provide a body joint or other anatomy with a desired energy absorption and/or transfer profile which complements the unique articulation at the target tissue.

The spring 168 of a bending spring assembly 166 can likewise be configured between one or more pivoting attachment structures 170, 172 (See FIGS. 26, 27). In a first approach, as shown in FIG. 26, one or both of the attachment structures 170, 172 are allowed to pivot about a pivot point. The pivoting action of the attachment structures 170, 172 of the device of FIG. 27 are constrained by stops 174.

Each of the previously and for that matter, hereinafter disclosed embodiments can incorporate or cooperate with sensing mechanisms adapted to provide loading information concerning the tissues being treated. Thus, it is contemplated that the various pressured sensing mechanisms available can be placed upon the devices of the present invention. Such sensors can be configured to provide information about the efficacy of the energy manipulating device of the present invention and whether adjustments are necessary. Similarly, sensors can be placed on anatomy to provide information regarding loads being placed on the tissues themselves.

Furthermore, it is contemplated that drugs can be delivered to the interventional site targeted for energy manipulation. In this regard, the entirety of the subject matter disclosed in U.S. Publication No. 2007/0053963 is hereby incorporated by reference.

In other aspects, the present invention is embodied in a cam engagement assembly for energy manipulation. In this approach, the cam engagement assembly employs contacting elements, at least one of which has an eccentric contracting surface. The degree, duration and instance of elemental contact is controlled by the profile of the cam element or elements. Increased contact stress is contemplated between device elements when the body anatomy members are in extension. During flexion, the cam profile can be configured to ensure little or no engagement. The assembly can include a spring assembly that can be made to be adjusted, or exchanged, to tune the amount of energy absorption across anatomy.

Moreover, the surface engagement of the device can be created through multiple methods and can include such structure as wear-resistant bearing surfaces, ball bearings at a surface engagement site or a geared engagement. The mounting features of the device can be contained in separate mounting elements or incorporated into anatomy spring elements. The mounting design can further accommodate complex motion of a joint as it transitions from extension to flexion by allowing for rotation and pivoting, or through the use of compressible materials.

Various approaches to cam related energy manipulation are depicted in FIGS. 28-37. In a first embodiment (FIGS. 28 and 29), curved load bearing surfaces 202 are configured to rotate with respect to each other. The load bearing surfaces 202 are connected to attachment structure 204, 206 which in turn are affixed to body anatomy such as bones forming a joint. The connections between the load bearing surfaces 202 and attachment structures 204, 206 or between the attachment structures 204, 206 and the bone can be spring loaded or otherwise be comprised of flexible or elastic materials. As the body anatomy transitions between extension (FIG. 28) and flexion (FIG. 29), the energy bearing surfaces 202 move between varying degrees of engagement. In one aspect, it is contemplated that the greatest off-loading and energy manipulation occurs between loading members 202 when the body anatomy is in its extension configuration. The varying degrees of engagement are pre-selected to absorb energy between body members with the aim of reducing or eliminating pain. In this way, unique paths of motion can be preserved during an attempt at absorbing energy.

Another embodiment of a cam engagement assembly is shown in FIG. 30. In this approach, a center load bearing, joint section 208 is configured between a pair of spaced attachment brackets 210. Post members 212 provide rotation points to define an articulating engagement assembly. Various connecting points 214 can be further provided along the attachment bracket 210 to receive the post members 212 to thereby provide a means to readjust the assembly to fit a patient's needs. It is further contemplated that gearing structure (gears or gears and a rack) can be implemented into this embodiment to provide desired control between moving parts.

Another embodiment of a cam engagement assembly 215 of the present invention is depicted in FIGS. 31 and 32. In this approach, camming surfaces 216 are adapted to fit the natural contour of the body anatomy. In one aspect, the camming surfaces 216 are provided along substantially an entire range of surfaces of natural tissue which may come into contact. This structure is supplemented with a energy absorbing assembly 218 comprising springs or other structure for absorbing energy from areas of contact between the camming surfaces 216. Such an assembly 215 is affixed at a joint or other body anatomy employing approaches described herein.

Turning to FIG. 33, there is shown a cam engagement assembly 220 including a first concave camming surface 222 and a second convex camming surface 224. These surfaces are biased apart by a pair of springs 226 arranged in a parallel fashion. Each of the camming surfaces 222, 224 include cavities for receiving a portion of the springs 226. The springs 226 act as a energy absorbing structure and in combination with the convex and concave surfaces 222, 224 complements the action of the body parts to which the assembly is attached.

A similar combination of elements is disclosed in FIG. 34. Here, the camming surface assemblies 230 are at least at one end attached in a spring loaded arrangement 233 to brackets 232. A second camming surface 230 can be connected in a manner to allow pivoting between the camming surface 230 assembly and bracket 232 such as by providing a slotted connector 236. The brackets 232 are in turn affixed to body anatomy. Configured between the camming surface assemblies 230 is a load bearing spring assembly 238 which at opposing ends engages receiving holes formed in the camming surface assemblies 230.

As shown in FIG. 35, a ball bearing 240 can be strategically placed between camming surfaces 242 of a cam engagement assembly for the purpose of aiding the relative motion between the structures. Such an approach can be further incorporated into any of the disclosed assemblies. In one particular embodiment (FIGS. 36 and 37), a ball bearing 240 is placed between the anatomy of articulating members of a patient. Alternatively, a disc can be employed in like fashion. In either approach, the ball bearing structure 240 is supported by energy absorbing springs 242 which are in turn attached to attachment structure 246 mounted to patient anatomy.

A further aspect of the present invention is embodied in a segmented support assembly. Generally, this approach employs multiple elements that align and mate to provide column support as desired, such as during extension of loading parts. Thus, in one aspect, adjacent elements forming a segmented support assembly can be constrained by an adjacent element in a variable fashion to accommodate the complex motion of articulating members. The amount of energy manipulation is adjusted by mounting or attaching components via spring or dampening assemblies.

With reference to FIGS. 38 and 39, there is shown one embodiment of a segmented support assembly 300. Fixation attachment structures 302 are provided to attach the assembly to patient anatomy. Medially positioned pivot points 304 in combination with adjustable spacers 306 define a segmented load bearing member and provide desired off-loading as well as multi-dimensional flexibility permitting the patient anatomy to articulate freely. Being adjustable, the spacers 306 function to facilitate alignment. In one particular aspect, at least one fixation attachment structure 302 can include a slotted receiving trough 306 sized to receive one terminal end 308 of the segmented load bearing member, the terminal end 308 slideably engaging the slot.

The segmented load bearing member can assume various shapes and forms. These approaches incorporate multiple, mating elements which provide columnar support while facilitating multi-dimensional movement. Such approaches are shown in FIGS. 40-45. As depicted in FIG. 40, disc-like members 310 are connected in a series via interconnecting structures 312 contemplated to permit three-dimensional translation between adjacently arranged discs 310. While three-dimensional motion is contemplated, the degree of motion is constrained by the members defining the segmented load bearing member. Accordingly, there can be limited axial compression of the members so that there is a desired amount of columnar support. Likewise, lateral pivoting of the members is limited by the geometry of the adjacent discs. The lateral pivoting can be selected to permit and complement the unique articulation of a particular patient's anatomy.

The structure defining a segmented load bearing member can assume relatively complex geometry. That is, various embodiments of interlocking links 314 can form a segmented load bearing member 316 (See FIGS. 41-46). Such links 314 can be held within a sheath 318 (FIGS. 41 and 45) or can be locked together to permit articulation without the need for an outer sheath (FIGS. 42-44 and 46). In a further aspect (See FIG. 46 for example), certain designs of the links 314 can include a projection 320, a number of which are received within a variable shaped slot 322 of an adjacent link. The variable staged slot 322 can further include a narrower section 324 which is sized and shaped to engage the projection 320 in a manner to both absorb loads as well as constrain articulating motion.

Furthermore, as shown in FIG. 47, the links 314 of a segmented section of a load bearing member 316 can embody variably shaped links 314. That is, the geometry of the links 314 can vary along a length of a load bearing member 316 to thereby provide differing articulation at various points. Moreover, the assembly can incorporate one or more springs 326 designed to facilitate desired energy absorption and/or dampening.

Other examples of assemblies including segmented load sharing linkages in combination with spring assemblies are shown in FIGS. 48-52. In each of these embodiments, springs 326 can be placed at one or more ends of the segmented load bearing members 316. It may be convenient to configure the springs 320 within attachment structures 302 employed to anchor the assembly to body anatomy. Springs 320 can also be placed along other portions of the assembly to achieve desired effects.

In yet another embodiment (FIGS. 53 and 54), the assembly is provided with slotted structure 330 rather than springs. The slotted structure 330 can be configured within the attachment structure 302 and be both generally vertical (FIG. 53) or generally horizontal (FIG. 54). An adjustment screw 332 or similar structure can further be provided to permit adjustment of the attachment structure relative to patient anatomy and to the segmented load bearing structure 316.

Other of segmented support assemblies of the present invention employ articulating linkages rather than interlocking links to provide desired results (See FIGS. 55-59). The various contemplated articulate linkages 334 can have a myriad of shapes and sizes and can include one or more points of articulation 336. Opposed ends of the linkages 334 are affixed to body anatomy in varying ways as well. As with all of the disclosed embodiments, mounting structure of one approach can be substituted for another and thus, the load bearing assemblies can be surface mounted to anatomy or partially buried therewithin. Moreover, the linkages can be sheathed (See FIG. 56) or can lack sheathing.

In yet another specific approach, the present invention employs piston support to accomplish desired load manipulation. In general, these embodiments include an axially mobile member which translates in a defined linear path. A compressible spring can be included to facilitate energy absorption and transfer and the assembly can further include structure permitting articulation between the piston subassembly and the body anatomy.

A simplified approach involving a piston support, load manipulation assembly 400 is depicted in FIGS. 60 and 61. In this embodiment, the piston member 402 is highly laterally flexible but also sufficiently longitudinally rigid to thereby both bend with the articulation of body members as well as absorb compression forces when the body members are in extension. One or more cylinders 404 are configured to accept longitudinal translation of the piston 402.

A piston support assembly 400 can further include springs 406 to aid in the load manipulation being sought (See FIGS. 62 and 63). Such springs 406 can be placed within an attachment cylinder 404 (FIG. 63) or can be additionally or alternatively placed about the piston assembly 402. Moreover, the piston assembly 402 can assume a complex geometry which includes both pivot points 408 and/or curvilinear portions 410. As in all of the disclosed embodiments, the structure can be affixed to body anatomy so that it spans a joint between articulating members.

Further embodiments of piston-based load bearing members are disclosed in FIGS. 64-70. FIG. 64 discloses an arrangement when a spring 402 spans the length of the piston member 402 and within spaced cylinders 404. FIG. 65 employs a piston member 402 which additionally includes bending spring structures for energy manipulation. FIGS. 66 and 67 depict a piston assembly 402 including a knurled outer surface and is further contemplated to include means for adjusting the strength of its loading capabilities by rotating the piston with respect to the cylinder. FIG. 68 shows an assembly which includes a spring 406 configured about the piston 402 having a stepped profile and between a cylinder 404 and a pair of stops 412. This assembly is also contemplated to be adjustable between high and low spring tensions.

A piston support based assembly 400 can also include a plurality of telescoping members 414 arranged longitudinally. Thus, certain of the circumferentially arranged telescoping members act both as pistons and cylinders for adjacent structure. By varying the energy which adjacent telescopic members 414 can bear, a desired energy absorbing profile can be provided by the structure to thereby absorb energy in a desired sequence.

As previously described, the energy absorbing assemblies of the present invention can be surface mounted upon anatomy or can be inserted completely or partially within the target tissue. As shown in FIGS. 71 and 72, a piston based, energy manipulation assembly 400 having one or more cylinders 404 receiving a piston 402 can be substantially completely implanted within a member defining a target tissue. The portions extending out from a surface of the tissue provide the energy absorbing characteristics needed for a particular application. The assemblies 400 can also be configured to span articulating body members and include a portion of the cylinder 404 being buried within body tissue as shown in FIGS. 73 and 74.

Structure which is believed to be particularly suited for the situations depicted in FIGS. 73 and 74 is shown in FIG. 75. Here, the energy absorbing assembly 402 includes a mid-section characterized by a piston having bending spring qualities and further includes collars 416 which are configured to rotate with respect to the piston. The collars 416 are also sized and shaped to be placed into a reciprocating motion with a cylinder.

With reference to FIGS. 76 and 77, the collars 416 can further include a washer and bearing arrangement which permits rotation of the collar 416 and the piston or end 402. Further, a screw assembly can be employed to connect the mid-section of the piston assembly with the collar 416. A spring 422 can be further provided within the collar 416 (See FIG. 77) to accept loads. The assembly 400 is then threaded within an attachment structure 424 and affixed to or within body tissue.

In a further modification to the approach in FIGS. 76 and 77, it is contemplated that inner 430 and outer members 432 of the collar assembly 416 can be adjustable post-implant. In a first embodiment (FIG. 78), the collar assembly 416 can include a percutaneously accessible adjustment screw 434 which controls the relative positions between the inner and outer members 430, 432. One or more of the inner and outer housings 430, 432 can alternatively be equipped with a gear surface 436 that is accessible by a percutaneous gear shaft tool 438. The tool 438 includes a terminal end 440 configured with a gear surface complementary to that of the gear surface formed on the collar assembly 416. In this way, tension as well as spacing of the components of a energy manipulation assembly can be altered or corrected as needed.

A sheathed energy manipulation assembly 440 incorporating various aspects of the present invention is shown in FIGS. 80-84. In this embodiment, ends of the assembly are reciprocally mounted within body tissue. The length of the device is encased in a sheath 442. It is to be recognized that various of the contemplated energy manipulation assemblies can be encased to thereby provide smooth surfaces which are less traumatic to body tissue. Moreover, as shown in the figures, one or more spring assemblies 444 can be placed about and in apposition with load bearing structure.

As best seen in FIGS. 84 and 85, the piston-type bearing assembly can further include an adjustment screw 450 arranged in a parallel fashion with respect to other energy absorbing structure to alter the effect of the same. Again, it is anticipated that such adjustment structure can be accessed percutaneously after the load bearing assembly is placed at or within a target tissue.

Yet another embodiment of the present invention is disclosed in FIG. 86. In this assembly, a pair of spaced attachment assemblies 460 include projections 462 for engaging the tissue to be treated. The attachment assemblies 460 further each include locking side screws 464 as well as a rotatable access screw head 465 which operate to affect a longitudinal position (advancement and retraction) of a threaded shaft with a ball-tipped terminal end 466. Configured between the longitudinally spaced shafts 466 is a piston and cylinder assembly 468 having opposed ends 470 with a socket sized to receive the ball portion of the threaded shaft 466. A first spring 472 is contained within the cylinder 474 of the assembly. A second spring 476 is coaxially arranged about the threaded shafts 466 and piston and cylinder assembly 468. Further, a sheath 476 is placed about these subassemblies from one attachment assembly to another 460. Thus, this embodiment of a energy manipulation assembly provides both energy absorption as well as multi-dimensional translation to permit body anatomy articulation.

Yet further details of useful energy manipulation are disclosed in FIGS. 87-94. A bi-lateral energy manipulation assembly 480 includes a pair of laterally configured shafts 482, at the terminal ends of which are connected a single energy absorbing member 484. The energy absorbing member 484 can include a piston and spring assembly arranged and the shafts can extend a full width and length of the tissue being treated. Further, the laterally configured shafts 482 can include a longitudinally extending trough 486 employed to selectively engage complementary surfaces of the energy absorbing member assemblies 484. Also, as best seen in FIG. 88, tissue inserts 488 in the form of collars are contemplated to receive at least a portion of a length of the shafts 482. Such inserts 488 as well as other surfaces of the various disclosed embodiments and approaches can include a bone-ingrowth coating or texture.

A related unilateral mounted device is shown in FIG. 92. In this approach, the shafts 482 extend less than a full width of the body anatomy but otherwise include a piston-based energy manipulation assembly 484. Once again, the members defining the piston assembly 484 can be sheathed with encasing structure 486 and can pivot about end points 488. The encasing structure 486 can be applied to various structures of the disclosed embodiments and can be formed from PTFE, ePTFE, Dacron, Polypropylene, Polyethylene, or woven materials such as silk. This structure 486 can also be created from bioabsorbable material and can be drug loaded or impregnated with silver or other agents capable of stimulation or reducing inflammation. The piston subassembly can further include a biasing spring 490 configured about a piston 492 and placed in a position with an internal cylindrical sleeve 494. Within the internal cylindrical sleeve 494 can be configured a further energy absorbing structure 496 such as a simple bending, columnar spring or a conventional helical spring (See FIGS. 93 and 94).

Moreover, with reference to FIG. 93, the piston subassembly 484 can include a platform 498, the position of which is adjustable by turning a central screw shaft 500. Again, it is contemplated that the screw shaft 500 be percutaneously accessed for ease of adjustment. Further, the dampening element can also involve a fluid-dampening system (FIGS. 93 and 94). Holes 502 formed in an end of position 492 effect a slow movement of fluid 504 through the assembly to prevent rapid changes in velocity.

Thus, the energy absorbing substructure 496 is engaged only at maximal compression of the assembly and at all other times remains free within the device.

Turning now to FIGS. 95-103, further embodiments of structure incorporating features of the present invention are depicted. In particular, the energy manipulation assembly 510 shown in FIGS. 95 and 96 includes first and second attachment structures 512, 514 having contours selected to match outer surfaces of body anatomy. An energy absorbing member 516 includes a pair of spaced ends each being pivotably attached to one attachment structure. The connection to the attachment structures 512, 514 as well as the energy absorption member 516 can further be sheathed in encasing structure 518 as described above. In this way, the overall structure assumes a low profile and generally atraumatic assembly which tends to cooperate with body anatomy.

In yet another approach (See FIG. 97), an energy manipulation assembly 520 of the present invention can incorporate into a first of a pair of attachment structures 522, 524 for mounting to body anatomy, an energy manipulation subassembly 526. Here, the attachment structure 522 includes a first end for mounting to body anatomy as well as a midsection employing a spring assembly 528 and a second end 530 including a slotted and cam assembly for engaging the second attachment structure.

Other bilateral energy manipulation assemblies 532 incorporating spring subassemblies are shown in FIGS. 98 and 99. In each, pivoting structure is employed to connect energy manipulation assemblies 534 including springs 536 mounted about central rods 538, to body anatomy attachment structures 540. Again, in order to provide more atraumatic surfaces for contacting body tissue, portions of these approaches can be sheathed in encasing material 542. The manner in which such energy manipulation assemblies cooperate with the natural articulation of body joints is shown in FIGS. 100 and 101.

FIGS. 102 and 103 depict an approach where the energy manipulation assembly 546 includes a first part 548 and a second part 550, the first and second parts only engaging when the body anatomy approaches an aligned configuration. In this way, energy manipulation is achieved in tension but not in flexion.

Various further details of mounting or attachment structure are shown in FIGS. 104 and 105. Again, the present invention contemplates attachment structure 554 which follows the exterior contour of anatomy such as bones to which the attachment structure 554 is mounted. Moreover, such attachment structure 554 can extend longitudinally varying distances along the body anatomy. Furthermore, the contemplated attachment structures 556 can extend a substantial lateral distance along body anatomy as well as longitudinally to define various geometries. In one aspect, the attachment structures can assume a modified Y-shape.

With reference to FIG. 106, still yet a further embodiment of an energy manipulation assembly 560 incorporating various features of the present invention is shown. Configured between spaced attachment or body anatomy structures 562 is a complex energy absorption subassembly 564. An adjustment mechanism 566 can be affixed to one attachment structure 562 so that the degree of energy manipulation can be modified as needed. In the approach depicted, the adjustment mechanism 566 includes a slotted section 568 that receives a screw 570 which can be manipulated to allow the assembly to slide towards and away from the energy absorbing member 564. The energy absorbing member further includes a rotating, arcuate arm 572 which alternatively engages the attachment structure 562 having the adjustment subassembly 566, and a spring or otherwise biased projection 574. The various geometries and dimensions of the components of this approach are selected to accomplish desired load manipulation cooperating with natural articulation of the body anatomy being treated.

Turning now to FIGS. 107-109, the forces occurring between body joints is discussed. The arrows 580 of FIG. 107 depict the forces occurring between adjacent members of a body joint lacking an energy manipulation assembly of the present invention. However, in body anatomy incorporating the present invention, less forces are transferred to the bones and cartilage of the members defining the joint. Where the body joint is treated with the foregoing described energy manipulating assemblies of the present invention 582, a degree of the forces between body members is absorbed by the energy manipulating assembly (depicted as arrows 584). Accordingly, less force 586 is placed on natural body anatomy.

FIGS. 110-112 depicts the relation between force (F) and displacement (S) between members of a body joint (where mass is constant). In a rigid body system (FIG. 110) which does not incorporate aspects of the present invention, there is no displacement and no energy absorption. In an energy manipulating system incorporating a single linear spring (FIG. 111), energy is absorbed in proportion to a spring constant (spring stiffness). The energy absorbed is represented by the shaded area 590 below the curve. As shown in FIG. 112, where a spring and dampener is used in combination, the energy absorbed 590 is a function of the spring constant and the dampener. It is these relationships which are considered in developing desired energy manipulating characteristics.

Also considered are the forces existing through the flexion and extension through an articulation cycle of anatomy to be treated. Using the gait cycle of the legs of a human as an example, both the joint force and flexion/extension angle in degrees can be plotted versus the percentage of the gait cycle completed. A normal or expected relationship 600 of vertical forces generated through the gait cycle is depicted in each of FIGS. 113-117. Also depicted in the FIGS. is the flexion/extension angle 602. The expected relationship 600 of vertical forces during the gait cycle can be altered using certain of the embodiments of the energy manipulation assemblies of the present invention. As shown in FIG. 114, the energy manipulation assemblies can absorb energy by a fixed proportion during a portion of the gait cycle. This is reflected by curve 604. Moreover, energy can be both absorbed and dampened as represented by curve 606 of FIG. 115 or alternatively, energy can be absorbed only above a fixed value as represented by curve 608 of FIG. 116. Additionally, as reflected by curve 610 of FIG. 117, energy can be absorbed in a fixed range of motion. It is to be recognized, however, that each of or one or more of these types of energy absorption can be combined in a desired system.

By way of example, the energy manipulation assembly 612 depicted in FIG. 118 could be employed to provide varying degrees of energy manipulation during a gait cycle and patient healing. The energy manipulation member 614 can include a spring 618 which slides within a slider 620 during normal motion. At first the spring 618 does not engage but at some point after implantation for example three weeks, a rotation tab 622 is locked within a slot 624. At that point, the sliding spring engages the tab 622 at key stages of gait and absorbs desired amounts of energy.

As mentioned above, the present invention has applications to various parts of the body. As shown in FIGS. 119 and 120, an energy manipulation assembly 630 can be placed within the cavity 632 between the acromiom 634 and the humerus 636 bones. Although various approaches are contemplated, in one aspect the energy manipulation assembly can include a spring loaded body 638 between fixation points 640. A bearing surface 642 in the form of a ball bearing is further contemplated as is a spring compression adjustment subassembly 644.

In an application to the foot (See FIG. 121), an energy manipulation assembly 646 can be placed between the tibia 648 and the calcareous 650 bones to address problems with the ankle. Such an approach can help alleviate pain as well as address symptoms associated with a condition referred to as drop foot. Thus, the assembly 646 can be configured to accomplish a lifting motion on the foot.

Applications to the hand and finger are also contemplated (FIGS. 122 and 123). Here, one or more load manipulating assemblies 660 can be positioned between distal 662 and middle 664 phalanges as well as between middle 664 and proximal 666 phalanges. Moreover, distraction units 668 can be placed between adjacent phalanges 670 to treat various conditions.

Moreover, the present invention has applications to the spine (See FIGS. 124 and 125). Accordingly, a load sharing or energy manipulating device 680 can be attached to and placed between vertebra 682 to off-load a disc 684. The energy manipulation device 680 can be attached to the side of the vertebra 682 (FIG. 124) or can be affixed to facets (FIG. 125). Moreover, the device 680 (See FIG. 124) can include various of the previously described features such as adjustment nut 686 effecting the action of a shock absorber spring 688. A load transfer unit 690 can be further provided to include another spring 692 as well as adjustment nut 694. A pair of fixating attachment structures 696 are further provided for mounted to body tissue.

It is to be borne in mind that each of the disclosed various structures can be interchangeable with or substituted for other structures. Thus, aspects of each of the bending spring, cam engagement, segmented support and piston support assemblies can be employed across approaches. Moreover, the various manners of engaging energy absorbing structure with attachment structure and attachment structures to body anatomy can be utilized in each approach. Also, one or more of the various disclosed assemblies can be placed near a treatment site and at various angles with respect thereto. Pressure sensing and drug delivery approaches can also be implemented in each of the various disclosed embodiments.

Certain components of most embodiments of the present invention are designed for easy removal and, if necessary replacement while others are intended for permanent fixation. The permanent components are fixation components which have bony ingrowth promoting surfaces and are responsible for fixation of the system to the skeletal structure. The removable components include the mobile elements of the system such as the link members and/or the pivots or ball joints.

The advantages of this feature of the system include the ability to exchange key components of the system due to device failure, patient condition change or newer improved systems being available. Additionally if the patient subsequently requires further surgery the links may be removed to facilitate the additional procedure.

Further, certain of the contemplated mechanisms can be made to be completely disengaged mechanically and then brought into action under various conditions and during certain phases of the gait cycle. This discontinuous functionality—and the ability to tune that functionality to a particular patient's gait or pain is consequently a feature of the present invention.

Location of the permanent fixation components is important to fixation strength, ability to complete subsequent procedures, and location of pivots or ball joints. The fixation strength of the system, and therefore load bearing capacity, is dependent on the integrity of the bone onto which the attachment structure is fixed. To ensure strong fixation, in one embodiment, the fixation components span along the cortical bone and cancellous (or trabecular) bone. For example on the knee, the attachment structure would reside on the femoral shaft and extend down onto the trabecular bone on the end of the femur. Also, the system may utilize fixation on two cortical surfaces using through pins or bicortical screws.

A common joint procedure is joint replacement as previously described. The procedure of replacing a diseased joint includes resection of the surfaces of the joint and replacement with synthetic materials. To enable implantation of the energy absorbing system without impacting the potential to complete subsequent procedures (e.g., joint replacement) the permanent fixation components in a preferred embodiment are positioned at a location that does not compromise the total joint zone.

Many articulating joints are not simply pivot joints but involve complex multi-axis rotation and translation movements. To achieve its intended purpose, the energy absorber must accommodate these movements but also absorb and transfer energy during the required range of motion. To do so the joints on the device may be either in case A located at points on the bones of least motion, or in case B the joint mechanism must incorporate motion beyond simple uni-axial rotation or a combination of both.

In the case of A, the fixation components are positioned such that they orientate the attached device joint locations to preferred locations described by minimal or known motion characteristics. The device joint locations may be finely adjusted within a defined region on the fixation component to further optimize the device joint location. In the case of B) the device joint mechanism accommodates the positional changes and therefore can be placed on any distal point on the fixation component.

Therefore, the present invention provides a number of ways to treat body tissues and in particular, to absorb energy or manipulate forces to reduce pain. The present invention can be used throughout the body but have clear applications to articulating body structures such as joints.

Thus, it will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without parting from the spirit and scope of the invention. 

We claim:
 1. An implantable device useful for relieving knee pain that does not require modification of articular cartilage of a knee, the implantable device comprising: an implantable absorber configured to absorb at least a portion of a compressive load normally experienced by a natural knee joint, wherein the absorber includes first and second ends configured to be connected to bones on opposite sides of the knee below skin covering a side of the knee, and an elastomeric element or a spring positioned between said first and second ends, said elastomeric element or spring including one end which is unattached to the absorber; wherein said elastomeric element or spring is configured and arranged to resist compression of the device between said first and second ends and said unattached end of the absorber does not apply any substantial tensional forces to the knee.
 2. The device of claim 1, wherein the absorber is compliant.
 3. The device of claim 1, wherein the absorber comprises a spring.
 4. The device of claim 3, wherein the absorber further comprises a piston support.
 5. The device of claim 1, wherein the absorber is configured to be located extra-articularly.
 6. A method for relieving knee pain, the method comprising: implanting under skin at a side of a natural knee joint a device that does not require modification of articular cartilage, wherein when implanted the device includes an elastomeric element or a spring which absorbs at least a portion of a compressive load normally experienced by the natural knee joint, wherein said elastomeric element or spring includes one end which is unattached to the absorber, and wherein said elastomeric element or spring is configured and arranged to act only in compression of the natural knee joint.
 7. The method of claim 6, wherein the device off-loads 1-40% of the load on the natural joint.
 8. The method of claim 6, comprising: relieving pain while preserving full motion of bones forming the natural knee joint.
 9. The method of claim 6, comprising: absorbing at least a portion of the energy normally experienced by the natural knee joint during gait.
 10. The method of claim 6, comprising: reducing load on at least a portion of the natural knee joint.
 11. The method of claim 6, comprising: transferring at least a portion of the energy normally experienced by the natural knee joint away from the natural knee joint.
 12. The method of claim 6, comprising: sharing with the natural knee joint at least a portion of the load normally experienced by the natural knee joint.
 13. The method of claim 6, comprising: dampening at least a portion of the load normally experienced by the natural knee joint.
 14. The method of claim 6, comprising: manipulating loads on portions of natural knee joint anatomy without overloading healthy surfaces.
 15. A method to reduce pain of a natural knee joint, the method comprising: implanting an energy absorber to reduce energy transferred through the natural knee joint, wherein the energy absorber is implanted extra-articularly under skin at a side of the natural knee and acts to absorb a compressive load, and wherein the energy absorber includes an elastomeric element or a spring configured and arranged to act only in compression of the natural knee joint, wherein said elastomeric element or spring includes one end which is unattached to the absorber.
 16. The method of claim 15, further comprising: transferring energy away from the natural knee joint.
 17. The method of claim 15 wherein the pain is caused by osteoarthritis of the natural knee joint.
 18. A method of reducing the pain associated with osteoarthritis in the knee, the method comprising: implanting under skin at a side of the knee an extra-articular energy absorber to reduce energy transferred through an osteoarthritic knee joint, wherein the energy absorber includes an elastomeric element or a spring which is configured and arranged to act only in compression of the osteoarthritic knee joint, wherein said elastomeric element or spring includes one end which is unattached to the absorber.
 19. The method of claim 18, wherein the absorber acts to absorb a compressive load normally experienced by the natural knee joint.
 20. The method of claim 19, wherein the absorber comprises a spring.
 21. The method of claim 18, wherein the absorber applies a force in a direction of distraction of the osteoarthritic knee joint.
 22. A method of reducing pain from an osteoarthritic knee joint comprising the steps of: implanting a device under a patient's skin in contact with bone in proximity to and on a side of the osteoarthritic knee joint, wherein the device is capable of absorbing energy during movement of the osteoarthritic knee joint such that energy transmitted across the osteoarthritic knee joint is redistributed resulting in lower energy being transmitted through the osteoarthritic knee joint itself; wherein the device includes an elastomeric element or a spring which is configured and arranged to act only in compression of the osteoarthritic knee joint, wherein said elastomeric element or spring includes one end which is unattached to the device.
 23. The method of claim 22, wherein the device acts to absorb a compressive load normally experienced by the osteoarthritic knee joint.
 24. The method of claim 23, wherein the absorber comprises a spring.
 25. The method of claim 22, wherein the device applies a force in a direction of distraction of the osteoarthritic knee joint. 